Fluid pressure operating means for boring machines



Oct. 8, 1935.

UID EI FLUID FRESSURB OPERATING MEANS FOR BORING MACHINES a g fi a 5 El; E :11 El 5 a E a 35 ZZZ a I U 33 L. c. SHIPPY El AL File d Sept 29, 1952 7 Shee ts-Sheet 1 FLUID PRESSURE OPERATING MEANS FOR BORING MACHINES 7 Sheets'-Sheet 2 Filed Sept. 29, 1952 L. C. SHIPPY ET AL Oct. 8, 1 935.

Oct. 8, 1935 L. c. SHIPPY El AL 2,016,654

FLUID PRESSURE OPERATING MEANS FOR BORING MACHINES Filed Sept 29, 1932 '7 Sheets-Sheet 3 Oct, 1935- c. SHIPPY El AL 2,016,654

FLUID PRESSURE OPERATING MEANS FOR BORING MACHiNES Filed Sept- 29, 19 3 v 7 Sheets-Sheet 4 Oct. 8, 1935. L., c. SHIPPY ET AL 5,

- FLUID PRESSURE OPERATING MEANS FOR BORING MACHINES Filed Sept. 29 1932 '7 Sheets-Sheet 6 11/? TANK 169 O2 203 ibo 1935 I L. c. SHIPPY ET AL I 1 FLUID PRESSURE OPERATING MEANS vFOR BORING MACHINES Filed Sept. 29, 1932 7 Sheets-Sheet 7 Patented Oct. 8, 1935 1 PATENT QFFICE rum) rarssuaa oraaarmo mums roa' some momma Leo C. Shippy, Lockport, N. Y, and John Q. Holmes, Anderson, Ind., assignors, by memo assignments, to General Motors Corporation, Detroit, Mich a corporation of Delaware Application September as, 1932, Serial No. 635,318

8 Claims.

This invention relates to automatic drilling or boring machines and moreparticularly to a machine for drilling or boring a cylindrical interior surface of a tubular member. 1

It is among the objectsof the present invention to provide a machine of the character described, whose operating tool is bodily moved in both directions by fluid pressure, and more particularly in such manner thatit slowly advances toward a workpiece and rapidly retracts therefrom in response to a single manipulation of a control member by theoperator of the machine.

Another object of the present invention is to provide means for varying the rate of reciprocatory movement of the operating tool.-

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings: V Fig. 1 is a perspective view showing portions of the right side and front elevations of the machine embodying the present invention.

Fig. 2 is a perspective view showing portions 7 of the left hand side and front of the machine.

Fig. 3 is a fragmentary side elevation partly in vertical longitudinal section.

Fig. 4 is a plan view of the machine looking in the direction of arrow 4 in Fig. 3.

Fig. 5 is an enlarged sectional view taken on the line 5-5 of Fig. 3.

Fig. 5a is a sectional view taken on the line 5a5a of Fig. 8.

Fig. 6 is a plan view of the workholder or chuck taken on the line 6-6 of Fig. 3. Fig. 6 is partly in section taken on the line Git-Ga of Fig. 12.

Fig. 7 is a sectional view taken on the line l-l of Fig. 6.

Fig. 7a is a sectional view taken on the line la-la of Fig. 6.

Fig. 8 isa front elevation of the control apparatus for the machine.

Fig. 9 isa side elevation thereof looking in the direction of arrow 9 in Fig. 8.

Fig. 10 is a plan view of the apparatus partly in section taken on the line |0|0 of Fig. 8.

Fig. 11 is a longitudinal sectional view taken on the line of Fig. 8, and ||a| la of Fig. 6,

,and shows the control apparatus in position for returning the boring machine to normal position, and for releasing the workfrom the chuck.

Fig. 12 is a view similar to Fig. 11 showing the control apparatus in position for causing the gear box 3| which is fast with the spindle frame.

chuck to grip the work and the boring machine to operate upon the same.

Fig. 13 is a diagrammatic view of afluid pressure system controlled by the control apparatus and bringing about the movement of the boring 6 member is secured by screws 23," The bearing 1 members 24 and 25 cooperate laterally to support and guide a spindleframe of cylindrical shape which supports at its upper end a gear box 3| upon the uppersideofwhichanelectric motor32is mounted in any suitablemanner. Motor32drivesashaft33 (see Fig. 3) carrying a gear 34 which meshes with j a gear 35, attached to a shaft 36, journaled in bearings 31 and 38, provided by the gear-box 3| and a gear-box cover 39 respectively, the latter of which provides a supporting basefor motor 32. 25 Shaft 36 drives a gear 40, meshing with a gear 4 I, attached to the upper end of a boring shaft or spindle 42, journaled in tapered roller bearings 43 and 44 which are secured to the spindle frame 30 in-proper manner as clearly shown in Fig. 3. It follows from the foregoing that the boring spindle 42 is longitudinally immovable with respect to the spindle frame 30, which itself is movable longitudinally within thebearing members 24 and 25. In order to prevent rotation of the spindle frame relative to the bearing members, a guide plate 45 of suitable shape, which. is secured by screws 48 to the frame 2| is received by correspondingly shaped guide portions provided by the 40 The spindle frame 30 is caused to descend or ascend under the action of suitable fluid under pressure in cylinder 23 such as oil for instance. This fluid actuates a piston 50 in said cylinder which transmits its movement through a connecting rod 5| to the gear box 3|. Connecting rod 5| is provided with a flathead 52, received in a recess 53 of the gearbox and retained therein by a nut 54. v

The boring spindle 42 carries at its lower end 50 a boringbit-hea'd 55 carrying one or more bits 56 for machining the interior of a workpiece A, clamped in a chuck 60, to be described, which is attached by screws 6| to a bracket 62 integral with the frame 2| which bracket provides a splash pan 55 69 for receiving liquid (such as water) used to cool the work and boring bits.

The chuck 60 which is shown in detail in Figs. 6, 7 and 7a comprises a frame 66, having a cylindrical bore 66 which receives chuck jaw frames 61 and 68, having cylindrical peripheries in which gear segments 69 and I0. respectively, are cut. Segments 69 and I mesh with racks II and I2, respectively, attached by rods I8 and I4, respectively, to pistons I and I6, respectively, (see Figs. 11 and 12) which are slidable in cylinders 17 and I8, respectively, provided by a cylinder block I9,

clamped between end plates 80 and 8| which are bolted to the chuck frame 65. Chuck jaw frame 6! is confined between the jaw frame 68 and the bracket 62. v Chuck jaw frame 68 is confined between the jaw frame 61 and a bottom plate 82, secured by screws 83 to the frame 65. Each of the jaw frames 61, 68 is provided with radial notches 84 each of which guides for radial movement a chuck jaw 85 having teeth for gripping the workpiece A. A part roller shaped portion 88 of each chuck jaw 85 is received by the socket portion 89 of glide shoe 90, which is adapted to engage with a stationary camming surface 9| provided by cam rings 9 Ia located in the frame 65. The glide shoes 90 are normally urged against the camming surfaces 9I by levers 92, pivotally receivedas at 93 in the heads of screws 94, threaded into the chuck jaw'frames 6! and 68, the free ends of the levers 92 beingreceived in notches 95 provided by the chuck jaws 85. Springs 96 which are seated in annular recesses 91 of the chuck jaw frames urge the levers 92 and therewith the chuck jaws 85 in such direction that the glide shoes 90 are maintained in engagement with the camming surfaces 9I. When the pistons I5 and I6 move toward the right as viewed in Figs. 6, 11 and 12, the frames 6! and 68 willrotate in the direction of the arrow98, thereby causing the glide shoes 90 to ride progressively toward those portions of the camming surfaces 9| which approach the center of the chuck, thereby causing the workpiece A to be firmly gripped by the jaws 85. When the pistons I5 and I6 move toward the left as viewed in Fig. 11, the motion of the chuck frames 61 and 68 will take place in the direction of the arrow 99, thereby causing the glide members 90 to ride progressively toward portions of the camming surfaces 9I which remove from the center of the chuck, whereupon the jaws will recede from the workpiece A and permit the latter to descend by gravity into a container I02 shown in Figs. 1 and 2.

As the frictional resistance encountered between the glide members 90 of the chuck jaws and the camming surfaces 9I= is a sliding friction the coefficient of which is less than the coefiicient of the static friction to be overcome first before the chuck jaw frames 61 and 68 can be started rotating in a counterclockwise direction as viewed in Fig. 6 to effect release of a clamped workpiece, another cylinder block I00 is provided (see Figs. 11 and 12) comprising two cylinders IOI and IOIa in axial alignment with cylinders 11 and I8, respectively, which receive pistons I05 and I06 respectively, adapted to aid pistons I5, I6 in their movement toward the left. Cylinder block I00 is clamped between end plates 8| and I03 all of which are bolted together as at I04. The pistons I05 and I06 are engaged by rods I01 and I08 re spectively, passing through stuffing boxes I09 and I I0 respectively, which are threaded into end wall 8|. When fluid pressure is admitted to the cylinders I1 and I8 to move the pistons therein toward the left as viewed in Fig. 11, the same fluid with annular chambers 266 and 261.

266 is formed by the camming surfaces 9| of the pressure will also be permitted to enter cylinders IM and IOIa thereby forcing the pistons therein toward the left which movement of the pistons I05 and I06-is transmitted through the rods I01 and I08 to the pistons I5 and I6 thereby aiding the 5 latter pistons in their movement which results in unclampingof the workpiece A. The manner in which the right sides of cylinders 11, I8 and IN, I0 I a communicate with the same fluid pressure in order to move the pistons in all these cylinders 10 toward the left will be described later.

With particular reference to Fig. 7 an oiler 260 is shown which is adapted to lubricate the sliding surfaces of the chuck jaws 85, the chuck jaw frames 6! and 68 and the cam rings 9Ia in order 15 to prevent rusting of these surfaces under the infiuence of the cooling water running past these surfaces from the splash pan 63. Extending into the oiler housing 26I are two tubes 262 and 263 which are closed on top and have an opening 264 20 in their cylindrical wall. These tubes 262 and 263 extend outside of the housing 26I andare threaded into ducts 264 and 265, respectively, in the bracket 65, which ducts are in communication Chamber 25 cam rings 9| (1, the external surface of chuck jaw frame 61, the bottom surface of bracket 62 and the top surface of bracket 65,.while chamber 26! is formed by the camming surfaces SI of cam rings 30 9Ia, the external surface of chuck jaw frame 68, the'plate 82 and the bottom surface of bracket 65. The oil level in housing 26I is supposed to be above the openings 264 in the tubes 262 and 263. During radial movements of all chuck jaws 85 35 toward the center of the chuck the oil containing chambers 266 and 261 are enlarged as can well be understood, and oil from the oiler will fill up the enlarged chambers. During the discharge of oil from the oiler, air is permitted to enter the oiler 40 through a check valve 268 on top of said oiler. During radial movement of the chuck jaws 85 away from the center of the chuck, the oil in the chambers 266 and 251 and in the oiler 260 is slightly compressed due to the fact that the air 45 overlying the oil supply in oiler 260 cannot escape through check valve 268 and is therefore slightly compressed. Some of the oil under pressure in the chambers 266 and 261 will therefore escape between the slidingsurfaces of the chuck jaws 50 85 and corresponding chuck jaw frames 61 and 68 with every retracting radial stroke of the chuck jaws. The cooling water has noaccess to the sliding surfaces of the chuck jaws and chuck jaw frames because there is a substantially permanent 55 coat of oil between these sliding surfaces. More important for a smooth operation of the chuck is the fact that the camming surfaces 9I are always in bodily contact with the oil in chambers 266 and 26! which oil appreciably reduces the considerable 80 static friction between glide shoes and camming surfaces 9|, which is to be overcome first when unclamping a workpiece.

The lower side of the piston 50 in cylinder 23 is permanently subjected to a fluid, preferably 65 oil because of its sealing quality, which is under substantially constant pressure. As best shown in Figs. 13 and 14 an oil supply I20 contained in a tank I2I communicates through a pipe I22 with the lower side of cylinder 23. Compressed 70 air I23 maintains the oil in the tank under pressure. An air compressor I24 of any suitable type forces compressed air into the tank I2I, said compressor being driven by an electric motor I25. As the pressure of the oil in tank I2I and the 75 will now be described with reference to Figs. 8

lower side of cylinder 23 should not exceed a certain value for reasons which will appear obmay be stated in advance that the pressure of the oil I20 which operates to lift the spindle frame 30 is less than the pressure of the fluid which is adapted to eifect descent of the same.

The control of the admission of pressure fluid to the upper chamber of cylinder 23, and to the chuck operating cylinders 11, 18 and IN, IOIa to 14 inclusive. To the front face I30 of the spindle frame guide member 25 is secured a plate I3I- which supports a valve body I32 to which end members I33 and I34 are secured, said end members providing brackets by which the body I32 is attached to the plate I3I. The plate I3I supports another valve body I35 having end ,members" I36 and I31 by which said valve body is attached-to plate I3 I. Valve body I32 is provided with a central bore I38 and valve body I35 with a similar bore I 39 which is in axial alignment with the bore I38. Valve body I32 receives a valve rod I40, providing cylindrical valves MI and I42 for conwith pipes I46, I41 andI48 respectively. A spring I49 tends to maintain the valve rod I40 in upper position shown in Fig. 11. The pipe I41 also communicates with the cylinder 23 between the piston 50 and a cylinder head 23a. Pipe ,I46 returns the pressure fluid to a fluid supply I50 which is preferably oil contained in a tank I5I as best shown in Fig. 13. Pipe I48 is connected with the high pressure side of a compression pump I52 whose lower pressure sidecommunicates with the oilsupply in tank I5I through a pipe I53. Compression pump I52 is driven by an electric motor I54. 9

The spring I49 which lifts the valve I4I surrounds a rod I60, attached to the valve I42 and adapted totransmit downward movement from said valve toa valve rod I6I which slides through valve body I35 and has cylindrical valves -I62 and I63 for controlling ports I64, I65, I66'and I61 communicating respectively, with pipes I60, I69, I10 and Ill. Pipe I68 communicates with a ,duct I12 in end plate M which is in communicainders 11 and 18 by a duct I18 and a groove I19 in said end plate. Pipe I1I leads back to a reservoir containing oil under low pressure or to the low pressure side of a compression pump (neither one shown). In the first case a compressor (not shown) forces oil under pressure from the reservoir into pipe I69, while in the second case the compression pump performs the same operation. Valve rod I6I is normally maintained in elevated position shown in Fig. 11, by a spring I80, surrounding a rod I8I, attached to the valve rod I6I. The valve rod I6I is provided with a central passage I82 communicating with the side passages I83 and I64. when the valve I6I moves upwardly these passages provide for the transfer of oil from that portion of the valve body I 36 which is above the valve I62 to that portion of the valve body I35 which is below the valve 5 I63, and vice versa, when valve rod I6I moves downwardly.

Normally the valve rods I40 andv I6I are in upper position as shown in Figs. 8, 9 and 11. When the valve rods are in this position the upper 10 end of the cylinder 23 is connected with the drain I46 as indicated by arrows, I65, I86 and I81.. Likewise the righthand sides of the cylinders 11, 13 and IOI, IOIa are connected with the high pressure supply pipe I69 as indicated by arrows 15 I and I89, whereuponthe pistons 15, 16 and I05; I06 move toward the left as viewed in Fig. 11, thereby causing the chuck jaws to be located in non-clamping position. To use the machine,

the operator will pass the workpiece A upwardly 20 through the central opening in the chuck 60 until the workpiece strikes a stop plate 60a which is attached to the bracket 62 as shown in Fig. '1. While maintaining the workpiece A. in this po-, sition with one hand, the operator pulls down on 25 a handle I90 (see Fig. 8) thereby causing a lever I9 I pivoted at I92 upon the plate I3 I, to move into lever I96 which is pivoted at I91 upon the plate 35 II, and urged by a spring pressed plunger I98 in a clockwise direction as viewed in Fig. 8, so that the latch I will engage the under side of the lever I9I to hold it in the position I9Ia. Movement of the valve rod I40 into the position 4 shown in Fig. 12 will cause the upper side of the cylinder 23 to be connected with the high pressure pipe I48 as indicated by arrows I99, 200 and 20I. The movement of the valve rod I6I into the position shown in Fig. 12 will cause the high pres- 45 sure pipe I69 to be connected with the left hand side of the cylinders 11 and 18 as indicated by arrows 202 and 203, in order to cause the pistons 15 and 16 to move toward the right as viewed in Fig. 12, thereby also moving pistons I05 and I06 50 toward .the right. Consequently, the workpiece A will be clamped in the chuck while the spindle frame 30 descends due to the force exerted upon the upper side of the piston 50 as indicated by arrows 204. As the spindle frame descends, the 55 rotating spindle 42 will cause the boring bits 56 to machine a, cylindrical surface upon the interior of the clamped workpiece A.

After the bits 56. have descended below the workpiece A, the spindle frame 30 will be caused 60 to ascend automatically, but the chuck 60 is not automatically released until after the boring bits 56 have ascended above. the workpiece.

Referring to Figs. 8 and 9 it will be noted that a latch bar 205 slidable in a bracket 206, is urged 05 by a bracket 2"! which is attached to the plate I3I. The rod 209'carries collars 2H and 2I2 which are adjustably secured thereto. By the time the boring bits 56 have descended below 5 the workpiece A the collar 2 will have descended slightly below the position 2I Ia shown in Fig. 8, in order to engage the latch lever I96 and to cause it to move counter-clockwise as viewed in Fig. 8 in order to move latch I95 from under- 10 ,neath lever I9I whereupon the spring I49 in valve body I32 will cause valve rod I40 to move upwardly, carrying with it lever I9I which moves from position I9Ia into the normal position shown in full lines in Fig. 8. The return of the 15 valve rod I40 to normal up position will allow the fluid pressure to flow from the cylinder 23 to the fluid supply in tank I5I in the manner indicated by arrows I85, I86 and I81 in Figs. 11 and 14. The lower surface of the piston 50 is con- 20 tinuously under substantially uniform fluid pressure and as soon as the valve rod I40 provides communication between the upper part of the cylinder 23 and the drain pipe 46, piston 50 and therewith the spindle frame 30 will ascend as 25 can be readily understood. By the time the boring bits 56 have arrived above the clamped workpiece A, the collar 2I2 will have engaged a bell-crank lever 2I3, pivoted at 2I4 upon the bracket 206, and move-the same clockwise as 3 viewed in Fig. 8, thereby causing its lever arm 2 I which is received by a notch 2 I6 in the latch bar 205 to move the latter toward the left as viewed in Fig. 8 so that it will clear the upper end of the valve rod I6I, whereupon the spring 35 I80 in valve body I35 will be permitted to return valve rod I6I into the position shown in Fig. 11. When this occurs the pistons 15,16 and I05, I06 will move from the position shown in Fig. 12 to that shown in Fig. 11, thereby retracting the 40 chuck jaws from the workpiece and permitting the same to descend by gravity into the receptacle I02.

If for any reason it is desired to stop downward movement of the boring spindle while in 45 operation, the operator may pull a handle 220 downwardly (see Fig. 8) to cause the lever I96 to move into a position for releasing the lever I9I, whereupon the spindle carrying frame 30 will ascend and the workpiece will be automati- 5 cally released from the chuck as can be readily understood from the foregoing.

Referring now more particularly to Figs. 13 and 14, the pump I52 is continuously driven by the motor I 54. As earlier explained, the fluid 55 delivered from the compression pump I52 serves only one side of piston 50 to effect descent of the same, and in order to prevent an undue increase of the pressure of the fluid delivered from the compression pump I 52 or a stalling of the 89 motor driven pump I52 when the piston 50 ascends, a pressure relief instrumentality in form of a fluid regulating valve 230 has been provided for automatically lay-passing the fluid in pipe I48 when under excessive pressure to the low 65 pressure supply in tank I5I. The reason for providing the fluid regulating valve 230 instead of a pressure responsive switch for stopping and restarting the motor I54 in response to predetermined pressures of the fluid in pipe I48 re- 7 sides in the fact that the applied former brings about more desirable results than the latter. The continuously flowing fluid under pressure in pipe I48 immediately causes piston 50 to descend {upon change of the course of said fluid into 75 the cylinder 23, while in the case of intermittent stops of pump I52 the pressure of the fluid in pipe I48 would rapidly sink due to uncontrollable leaks in the valves, etc., and the descent of the piston 50 would be appreciably delayed. Furthermore it would work hardship on the motor 5 I54 and the pump I52 if the same were repeatedly started under a substantial load. The relief valve 230 comprises a valve body or housing 23I providing axially aligned bores 232 and 233 of different diameter, and ports 234 and 234a. slidable within the bores 232 and 233 is a valve rod 235 which provides cylindrical valves 236 and 231 slidable within the bores 232 and 233 respectively. Valve body 23I is provided with end plates 238 and 239. A branch pipe240 of the 15 high'pressure pipe I48 communicates with a duct 24I, provided by valve body 23I, which in turn communicates with bore 232 through a duct 242 in the valve body and a groove 243, provided in end plate 238. Duct 24I also communicates with bore 234a. A branch pipe 244 of drain pipe I46 which is in communication with tank I5I, communicates with port 234 through a duct 245 of valve body 23I. In the position of the valves 236 and 231 shown in Fig. 13, piston 50 and 25 therewith the spindle frame is descending, the control apparatus is therefore in such position that the fluid in high pressure pipe I48 is free to pass to the upper side of piston 50. This fluid which is under substantially uniform 30 pressure during the descent of piston 50 is trans mitted through branch pipe 240, ducts 2, 242 and groove 243 to the left end surface of valve 236. The fluid pressure I20 is transmitted through a branch pipe 250 of pipe I22 to the right end surface of valve 231. It will be assumed for the sake of brevity that the pressure of the liquid I20 is substantially uniform in spite of the further compression of the already compressed air in tank I2I by the fluid which is pushed from the lower side of cylinder 23 into the tank I2I by the descending piston 50. During the descent of piston 50 it is desirable that no fluid in high pressure pipe I48 by-pass through the relief valve 230 to the liquid supply in tank I 5| the full charge of the compression pump I52 being necessary to serve the upper side of the piston during such descent. To

accomplish this desirable result the diameters of the valves 236 and 231 have been selected in con- 50 formity with the well known law that in order to keep a valve in balance the efifective areas have to be inversely proportional to the opposing pressures. It may be assumed that the fluid I20 which urges valve rod 235 toward the left 55 be substantially 100 pounds per square inch, and the pressure of the fluid in pipe I48 should not exceed 180 pounds per sq. in., it is then obvious from the foregoing that in order to keep the valve rod 235 in balance, the cross-sectional area of valve 236 has to be 10/18 or 5/9 of the cross-sectional area of the valve 231. As it is, however, desired that the valve rod 235 maintain the position shown in Fig. 13 it is necessary slightly to unbalance the valve rod by making the diameter of valve 231 slightly larger as can be readily understood. As soon as the control apparatus is automatically shifted in such position that communication between the high pressure pipe I48 and cylinder 23 is interrupted, the continuously driven compression pump I52 causes the pressure of the fluid in pipe I48 to increase, which increased pressure is also transmitted to the left end surface of valve 236 whereupon valve rod 235 is shifted from the position shown in Fig. 13 to that shown a Fig. 14 due to the fact that the pressure transmitted to the right end surface of valve 231 does not change. In the position of the valve rod 235 shown in Fig. 14, valve 231 provides communication between the high pressure pipe I48 and the drain pipe I46 through branch pipe 240, duct 2, port 234a, bore 233, port 234, duct 245 and branch pipe 244. In this manner the pressure of the fluid in high pressure pipe I48 never appreciably exceeds a predetermined pressure and no intermittent stopping and restarting of motor' I54 which drives pump I52 is necessary. As willbe noticed from Figs. 13 and 14, the-left end of valve 231 is slightly tapered so that the fluid in pipe I48 does not' suddenly communicate or be suddenly intercepted from communication with tank I5I thereby preventing undue strain to the pump due to otherwise occurring sudden changes in the pressure of the fluid in pipe I48. The advantage of having one side of piston '50 permanently exposed to fluid pressure resides in the fact thatthe piston 50 when exposed to the'fiuid pressure in the upper side of cylinder 23 slowly descends due to the permanent, counteracting fluid pressure I20 in the lower side of piston 50, and quickly ascends under the action of the same fluid pressure I20 as soon as the control apparatus is shifted in such position that the fluid in the upper side of cylinder 23 is allowed to flow back to supply tank I5I The last mentioned fluid when communicating with supply tank I5I ofiers hardly any resistance to the ascending piston 50. In this manner 'a slow workstroke of 'the boring frame 3 and a quick return stroke of the same has been accomplished with one control apparatus which controls the admission of fluid pressure to one side of cylinder 50 only.

The fluid pressure responsive relief valve230 not only eliminates intermittent stopping or starting of motor I54 but furthermore constitutes in combination with instrumentality I26, 9. means for adjusting the boring frame 30 to any desirable rate of reciprocatory movement. Suppose the instrumentality I26 were adjusted to P2=140 lbs. per sq. in., the pressure of the fluid I20 against the lower surface of piston 50 would then also be 140 lbs. per sq. in. and it follows from the foregoing that the piston and therewith the boring frame 30 would ascend quicker than before when a pressure of only 100 lbs. per sq. in. was applied. The rate of movement of the piston 50 downwardly would also be increased as emphasized by the following consideration. The valves 236 and 231 of the fluid relief valve 230 cause the maximum pressure of the fluid in high pressure pipe I48 to be increased to such an extent that the increased pressure P1 of the fluid would be in the same proportion to the pressure P2 as were the maximum pressures of the fluids before the increase in pressure. Using the earlier assumed values of the fluid pressures it follows that:

therefore P 180 X 140=252 lbs. per sq.' in.

Before the increase of the pressure of fluid I20, themaximum pressure causing piston 50 to descend was (180-100) lbs. per sq. in. less the resistance offered by the work to the tool. After the increase of the pressure of fluid I20 that maximum pressure, is (P1P2) or (252-140) =112 lbs. per sq. in. less the resistance offered by the work to the tool. Therefore, after the increase of the pressure of fluid I20 from lbs. per sq. in. to lbs. per sq. in., the pressure causin 5 the piston to ascend was increased 40 lbs. per sq. in. and the maximum pressure causing the piston to descend (not considering for simplicitys sake the resistance offered by the work to the tooll-was increased from 80 lbs. per sq. in. to 112 lbs. per sq. in., i. e. 32 lbs. per sq. in. Since the frictional resistance offered by the cylinder wall to the piston 50 is substantially uniform, it follows that an increase of pressure of the fluid I20 not only results in a quicker ascent of said 16 piston but also in a substantially proportional quicker descent of the same if the resistance offered by the work to the tool remains substantially the same. By selecting another ratio between the pressures of the fluids, a change of the 20 .rate of ascending movement of piston 50 will resuit in a more or less proportional change of the rate of descending movement of piston 50.

While the form of embodiment of the present invention as herein disclosed, constitutes a pre- 25 ferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In combination with a fluid pressure oper- 30 ated motor, means continuously delivering a first fluid under pressure adapted to operate the motor in one direction; means maintaining a second fluid under substantially constant and less pressure than the first fluid, said second fluid permanently 35 tending to operate the motor in the opposite direction; means for admitting the first fluid to and intercepting the same from the motor; and an instrumentality including a single valve subjected rection; means for admitting the first fluid to and 50 I intercepting the same from the motor; and an instrumentality including a single valve subjected to the pressures of both fluids and responsive to a preassigned pressure ratio between both fluids for by-passing the first fluid past the motor and re- 55 sponsive to another preassigned pressure ratio between both fluids for interrupting such bypassing.

3. In combination with a fluid pressure operated motor, means continuously delivering a first 60 fluid under pressure adapted tov operate the motor in one direction; means maintaining a second fluid under substantially constant and less pressure than the first fluid, said second fluid permanently tending to operate the motor in the 65 under pressure adapted to operate the motor in one direction; means maintaining a second fluid under substantially constant and less pressure than the first fluid, said second fluid permanently tending to operate the motor in the opposite direction; means for admitting the first fluid to and intercepting the same from the motor; and an instrumentality including a single valve subjected to the pressures of both fluids and actuated by the first fluid to by-pass the same past the motor when its pressure exceeds a preassigned value.

5. In combination with a fluid pressure operated motor, means continuously delivering a first fluid under pressure adapted to operate the motor in one direction; means maintaining a second fluid under substantially constant and less pressure than the first fluid, said second fluid permanently tending to operate the motor in the opposite direction; means for admitting the first fluid to and intercepting the same from the motor; and an instrumentality including a single valve subjected to both fluids and actuated by the first fluid to by-pass the same past the motor when its pressure exceeds a preassigned value, and actuated by the second fluid to interrupt such by-passing when the pressure of said first fluid drops below said preassigned value.

6. In combination with a fluid pressure operated motor, means maintaining a first fluid under substantially constant pressure, said fluid permanently tending to operate the motor in one direction;-

means continuously delivering a second fluid under higher pressure than the first fluid, said second fluid being adapted to operate the motor in the opposite direction; means for admitting the second fluid to and intercepting the same from the motor; and an instrumentality including a valve body in communication with the second fluid and a valve therein, one end face of said valve being exposed to the first fluid and the opposite end face thereof being exposed to the second fluid, these end faces being of such dimensions that the assigned value.

7. In combination with a fluid pressure operated motor, means maintaining a first fluid under substantially constant pressure, said fluid permanently tending to operate the motor in one direction; means continuously delivering a second fluid under higher pressure than the first fluid, said second fluid being adapted to operate the motor in the opposite direction; means for admitting the second fluid to and intercepting the same from the motor; and an instrumentality including a valve body in communication with the second fluid and a valve therein, one end face of said valve being exposed to the first fluid and the other end face thereof to the second fluid, the areas of these end faces being substantially inversely proportional to preassigned pressures of the two fluids whereby the valve is shifted into open position in which the pressure of the second fluid is relieved when the same exceeds a preassigned value, and is shifted into closed position when the pressure of said second fluid drops below said preassigned value.

8. In combination with a cylinder and a piston therein, means supplying high pressure fluid adapted to move the piston in one direction; a source of low pressure fluid permanently tending to move the piston in the opposite direction; means for admitting high pressure fluid to the cylinder and for simultaneously intercepting the high pressure fluid from the cylinder and venting the high pressure side thereof; an instrumentality including a single valve actuated by both fluids for maintaining a substantially constant ratio between the pressures of both fluids; and means for varying the pressure of one of the fluids at will.

LEO C. SHIPPY. JOHN Q. HOLMES. 

